Variable resistance control



Nov. 28, 1967 J. D. VAN BENTHUYSEN ETAL VARIABLE RESISTANCE CONTROL Filed July 27, 1964 FIGURE 4 47 3| 53 3 FIGURE 3 INVENTORS JOHN D. VAN BENTHUYSEN MERVIN E3. ARISMAN BY W ATTORNEY United States Patent 3,355,693 VARIABLE RESISTANCE CONTROL John D. Van Benthuysen and Mervin B. Arisman, Elkhart,

Ind, assignors to CTS Corporation, Elirhart, Ind, a corporation of Indiana Filed July 27, 1964, Ser. No. 385,113 3 Claims. (Cl. 338184) ABSTRACT OF THE DISCLOSURE A variable resistance control having an upper housing half and a lower housing half secured together to define a split housing. The lower housing half supports a collector ring and a resistance element having a pair of terminals connected to the ends thereof. The upper housing half comprises a cover having a depending skirt in overlapping relationship with a portion of the lower housing half. A Wall of the overlapped portion of the lower housing half is tapered toward the open end of the lower housing half todefine a reservoir containing bonding material securing the housing half together. A circumferential shoulder is provided at the base of the taper for supporting the skirt of the upper housing half. A driver having a pair of different size spindles is rotatably supported in the split housing concentric with the collector ring, and a contactor carried by the driver is constrained to rotate therewith for wiping the resistance element intermediate the ends thereof. The cover of the upper housing half is provided with an aperture rotatably supporting the larger of the two spindles of the driver and the smaller spindle is supported in a center hole in the lower housing half. In one of the embodiments, the larger spindle is provided with a center aperture having secured therein a stub shaft of a knob.

The present invention rel-ates to variable resistance controls and, more particularly, to a miniature variable resistance control of the semiprecision type.

In order to decrease the cost of electronic equipment, printed circuit mounted panels have become widely accepted during the past decade. As a consequence, the variable resistance controls mounted in the panels are designed to meet certain specifications so as to be compatible with the other components. Generally the controls must be of a specific diameter and provided with terminals readily insertable into the openings provided in the mounting panel. Whenever it is desirable to seal the housing of the control to protect the movable parts of the control from environmental and atmospheric conditions, it is advantageous to employ a housing of electrically insulating material. Constructing a housing of moldable insulating material is also advantageous in that the electrically conducting parts inside of the housing do not have to be insulated from a metal housing. The use of the insulating material for control housings also enables the designer of a control to have a minimum outside dimension and a maximum interior dimension for the movable parts. Althrough the prior art is replete with controls employing housings of insulating material, the problem of effectively sealing the housings and preventing the bonding material from being deposited on the movable parts inside of the housings has prevented universal acceptance of these controls. Consequently, elaborate means have been employed for securing the housing together, i.e., retaining springs for securing a cover over the open end of a housing. It would, therefore, be desirable to provide an improved control housing of electrically insulating material overcoming the limitation heretofore known.

As the physical size of the variable resistance control is decreased, it is generally more difiicult to assemble and support the rotatable driver of the control in the housing without employing elaborate structures and still seal the control housing from environmental and atmospheric conditions. It would, therefore, be desirable to provide an arrangementawherein a minimum number of parts are employed for rot-atably supporting a driver in a split housing of a sealed control and wherein the control may be assembled in a simple and facile manner.

Accordingly, it is an object of the present invention to provide a new and improved variable resistance control having the various desirable features set forth above.

Another object of the present invention is to provide a miniature variable resistance control enclosed in a split housing.

Still another object of the present invention is to provide a variable resistance control having a split housing wherein the bonding material employed for securing the housing halves together is prevented from entering into the cavity retaining the movable parts of the control.

An additional object of the present invention is to provide a miniature variable resistance control having a minimum number of parts in order that the control may be assembled in a simple and facile manner.

A further object of the present invention is to provide a miniature variable resistance control having a contactor provided with a pair of spaced rings and a reversely bent end portion disposed in a locating cavity in the driver for securing the contactor thereto.

A still further object of the present invention isto provide a split housing variable resistance control wherein the housing halves cooperate so as to form a reservoir of sui'hcient volume for retaining the "bonding material securing the halves together.

Yet another object of the present invention is to provide a housing for a variable resistance control having a driver provided with a pair of different diameter spindles, the larger of the spindles being rotatably supported in an aperture of the housing.

Yet an additional object of the present invention is to provide a split housing for a variable resistance control wherein approximately one half of one of the housing halves is in overlapping relationship with the other housing half.

Further objects and advantages of the present invention will become apparent as the following description proceeds, and the features of novelty characterizing the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

Briefly, the variable resistance control comprises an upper housing half and a lower housing half defining a split housing. The lower housing half supports a collector ring and a resistance element having a pair of terminals connected to the ends thereof. The upper housinghalf comprises a cover having a depending skirt in overlapping relationship with a portion of the lower housing half. A wall of the overlapped portion of the lower housing half is tapered toward the open end of the lower housing half to define a reservoir containing bonding material securing the housing half together. A circumferential shoulder is provided at the base of the taper for supporting the skirt of the upper housing half. A driver having a pair of dilierent size spindles is rotatably supported in the split housing concentric with the collector ring, and a contactor carried by the driver is constrained to rotate therewith for wiping the resistance element intermediate the ends thereof. The cover of the upper housing half is provided with an apetr-ure rotatably supporting the larger of the two spindles of the driver and the smaller spindle is supported in a center hole in the lower housing half. In one of the embodiments, the larger spindle is provided with a center aperture having secured therein a stub shaft of a knob.

For a better understanding of the present invention, reference may be had to the accompanying drawings wherein the same reference numerals have been applied to like parts and wherein:

FIGURE 1 is an isometric view of a variable resistance control built in accord with the present invention;

FIGURE 2 is an enlarged sectional view of the variable resistance control of FIGURE 1;

FIGURE 3 is an exploded view of the variable resistance control of FIGURE 1; and

FIGURE 4 is a side elevational view of another embodiment of a variable resistance control.

Referring now to the drawings, there is illustrated a variable resistance control, generally indicated at 10, comprising a split housing 11 and rotatable means for altering the resistance of the control.

Considering first the split housing 11 it comprises a lower housing half 12 of moldable electrically nonconducting material such as diallyl phthalate. As best seen in FIG- URES 2 and 3 of the drawings, the lower housing half comprises a base 13, an upstanding cylindrical side wall 14 open at one end 15, i.e., the open end thereof, and integral with the base 13. The inner surface of the base 13 of the lower housing half 12 is provided with an arcuate slot 16 having disposed therein a wirewound arcuate resistance element 17. As shown in the drawings, the resistance element 17 comprises a thin card 18 or mandrel having a fine nickel chrome alloy wire 19 wound thereon. The mandrel may, however, be oval or cylindrical whenever a resistance element having such cross section is desired. The slot 16 is of sufiicient width to receive such mandrels. A not-shown arcuate substrate of glass, plastic or ceramic such as alumina or steatite having a thin film resistance element of carbon or glass bonded material deposited on the flat surface thereof may also be deposed in the arcuate slot 16.

. Three terminals 20, 21 and 22 project downwardly from the base 13 of the lower housing half 12. The inner end 20a of terminal 20 is electrically connected by suitable means such as welding to a depending tab 23a of a collector ring 23 supported in the base 13 of the lower housing half 12. For the purpose of locating the collector ring 23 in the split housing 11, a pair of depending feet 23b integrally connected to the collector ring 23 are received in a pair of spaced holes 13a provided in the base 13. Terminals 21 and 22 are L-shaped and are preferably molded into the base 13 of the lower housing half 12 in a suitable manner. For certain constructions, however, it may be desirable to mount one of the legs of each of the terminals 21 and 22 in slots 13b as best shown in FIGURE 3 of the drawings and then fixedly secure the legs of the terminals 21 and 22 as well as terminal 20 to the base 13 with suitable electrically nonconducting thermosetting epoxy cement. Suitable foil strips 24 of electrically conductive material are employed for connecting the ends of the resistance element 17 to the terminals 21 and 22. The strips 24 are secured to the terminals by soldering, welding or the like.

The split housing 11 is also defined by an upper housing half 30 comprising an apertured cover 31 having a depending skirt 32 integrally connected therewith for closing the open end of the lower housing half 12 and overlapping a portion of the lower housing half. As best shown in FIGURE 2 of the drawings, the depending skirt 32 is of a uniform thickness and the overlapping portion of the lower housing half 12 is recessed at 12a in order that the outer surface of the skirt 32 is flush with the lower housing half 12 thereby providing a housing having an even cylindrical surface. In accord with the present invention, the wall 12b of the recess 12a extends upwardly a height substantially equal to the height of the depending skirt 32 and is tapered toward the open end 15 of the lower housing half 12 so as to provide a V-shaped slot .25 extending around the periphery of the split housing 11 4 when the upper housing half 30 is assembled to the lower housing half 12.

As described hereinafter the V-shaped slot 25 functions as a reservoir for retaining bonding material securing the housing halves together. More specifically, prior to the assembly of the upper housing half 30 to the lower housing half 12, a portion of the recess adjacent to the shoulder 12c is coated with a bonding material preferably a suitable electrically nonconductive epoxy cement. When the skirt 32 of the upper housing half 30 is positioned around the wall12b of the recess 12a, some of the bonding material exudes from the junction formed at the shoulder of the lower housing half and the lower edge of the depending skirt 32 and may be readily removed therefrom. Since the V-shaped slot 25 between the skirt 32 and the wall 12b of the recess 12a diverges toward the open end 15 thereof, the bonding material remains in the V-shaped slot 25 and is not exuded into the inner cavity of the split housing 11 upon the resistance element 17 and associated parts disposed inside of the housing. Essentially the volume of the V-shaped slot 25 is sufficient to contain all of the bonding material except that portion removed at the junction. Moreover, by tapering the recess toward the open end 15 of the lower housing half 12, a better fit is obtained between the skirt 32 of the upper housing half thereby assuring that the aperture 33 in the cover 31 of the upper housing half 30 is concentric with the center hole 34 in the base 13 of the lower housing half 12. Such alignment assures that the rotatable means wiping the resistance element 17 is properly mounted inside of the split housing 11.

For the purpose of wiping the resistance element intermediate the ends, the rotatable means comprises a driver 40 of suitable electrically nonconduct-ive material such as diallyl phthalate. The driver 40 is provided with a pair of spindles 41 and 42, one of the spindles 41 being of a smaller diameter than the other spindle 42 and journaled in the center hole provided in the base 13 of the lower housing half. The other spindle 42 is journaled in the aperture 33 provided in the cover 31 of the upper housing half 30. Preferably, the other spindle, -i.e., the larger diameter spindle, terminates flush with the outer surface of the cover 31. -In order to limit the angular rotation of the driver, a stop 43 extends radially from the driver and is adapted to engage a stop member 44 integral with the upstanding cylindrical side wall 14 of the lower housing half 12 and disposed between the ends of the resistance element 17 as best seen in FIGURE 3 of the drawings.

A contactor 45 engaging the resistance element 17 is mounted on the driver and constrained to rotate therewith for wiping the resistance element intermediate the ends thereof. Preferably, the contactor comprises a base portion 46 having a reversely bent end portion 47 extending outwardly therefrom. for securing the contactor 45 to the driver 40. The reversely bent end portion 47 of the contactor is disposed in a slot 48 provided in the driver (see FIGURE 2, the width of the slot 48 being of a dimension slightly less than the width of the reversely bent end portion for rigidly securing the contactor to the driver. Further, the distal end 47a of the reversely bent end portion 47 is forced into a side wall of the slot 48 thereby preventing disassembly of the contactor 45 from the driver during assembly of the driver in the split housing 11. An inner arcuate ring 49 defining the collector ring contact arm extends from the base portion 46 in a direction opposite to the reversely bent end portion 47 and encircles one of the spindles 41 for centering the contactor with the driver, and an outer arcuate ring 50 defining the resistance element contact arm extends from the base portion 46 in spaced relationship to the inner arcuate ring 49 forming an arcuate slot between the two arcu'ate rings of the contactor 4,5. A collcctor ring contact 51 defined by a circular depression or dimple in the inner arcuate ring 49 engages the collector ring 23 and an element contact 52 integral with the outer arcuate ring 50 and diametrically opposite from the base portion 46 provides maximum spring range of the contact arm carrying the contact 52 as it is wiped intermediate the ends of the resistance element. Preferably and as illustrated in the drawings, the resistance element contact arm extends upwardly so as to engage the curved portion of the resistance element thereby further increasing the length of the contact arm and the spring range.

Preferably and as illustrated in FIGURE 2 of the drawings, an O ring 53 of resilient material is mounted over the larger spindle 42 for sealing the aperture 33 of the split housing 11. The proper rotational torque of the driver may also be altered by changing the thickness or hardness of the O ring. A circular rim 35 depending from the inner surface of the cover 31 circumposes the O ring 53 and restricts movement of the O ring 53 as the driver is rotated.

The control is adjusted or preset by inserting an appropriate tool, for example, a screw driver, into a narrow slot 35 provided in the end of the larger spindle 42. Suitable indicia, such as a plurality of radial indicator marks 37, are provided on the cover 31 for accurately and rapidly presetting the resistance value of the control 10. To assure that the indicia on the cover 31 of the upper housing half 30 are properly oriented with the stop member 44, a locating pin 38 projects upwardly from the lower housing half 12 and is received in a locating pin hole 39 in the cover 31 of the upper housing half.

Whenever a thumb knob type control 110 is desired as shown in FIGURE 4 of the drawings, the larger spindle of the driver is provided with a central opening for receiving a portion of a stub shaft 111 depending from a knob 112. The stub shaft 111 is fixedly secured to the end of the larger spindle with a suitable epoxy cement. A slot may also be provided in the knob 112 thereby permitting either thumb or tool adjustment of the control 110. Suitable undulations 113 are provided on the periphery of the knob 112 to facilitate gripping thereof. With the above described arrangemenuthe assembly and operation of the miniature variable resistance control will be readily understood and no further discussion is included herewith.

While there has been illustrated and described what is e at present considered to be a preferred embodiment of the present invention, and a single modification thereof, it will be appreciated that numerous changes and modifications are likely to occur to those skilled in the art, and it is intended in the appended claims to cover all those changes and modifications which fall within the true spirit and scope of the present invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. In a variable resistance control having a resistance element, and a contactor for wiping the resistance element intermediate the ends thereof, the improvement comprising a split housing comprising a first housing means provided with an upstanding side wall open at one end and closed at the other end to define a lower housing half supporting the resistance element and the contactor, a recess extending around the periphery of the upstanding side wall adjacent to the one end of the first housing means and terminating at a shoulder disposed between the one end and the other end of the first housing means, one wall of the recess being tapered toward the one end of the first housing means, a second housing means closing the one end of the first housing means and having a depending skirt in overlapping relationship with a portion of the upstanding side wall of the first housing means to define an upper housing half, the skirt of the second housing means abutting against the shoulder of the first housing means and cooperating with the recess to define a reservoir having a V-shaped cross section, the reservoir having a greater dimension at the one end of the upstanding side wall than at the shoulder, and bonding means securing the second means to the first means, the reservoir being of suflicient volume for retaining the bonding material thereby preventing exudation of the bonding means into the interior of the split housing of the control.

2. In a variable resistance control, the combination of a hollow cylindrical lower housing half having a closure wall at one end thereof and open at the other end thereof, a resistance element supported in the lower housing half, an upper cylindrical housing half provided with an apertured cover and a depending skirt closing the other end of the lower housing half, a recess extending around the outer periphery of the lower housing half and terrninating at a shoulder spaced from the closure wall, the depth of the recess at the shoulder being substantially equal to the thickness of the skirt, the skirt extending around a wall of the recess, the wall of the recess being of a height slightly less than the height of the depending skirt and tapered toward the other end of the lower housing half to define a V-shaped reservoir, means rotatably mounted in the aperture of the cover of the upper housing half and in a center hole provided in the closure wall of the lower housing half for wiping the resistance element intermediate the ends thereof, and bonding means in the V-shaped reservoir securing the housing halves together.

3. The variable resistance control of claim 2, wherein the means rotatably mounted in the aperture of the cover comprises a driver having a pair of different diameter spindles, the smaller diameter spindle being journaled in a center hole provided in the base of the lower housing half, the larger diameter spindle being journaled in the aperture provided in the cover, and a thumb knob secured to the larger diameter spindle for rotating the driver.

References Cited UNITED STATES PATENTS 2,525,993 10/1950 Youngbeck et al. 338163 X 2,717,944- 9/1955 Daily et al. 338174 X 2,943,288 6/1960 Budd 338-174 X 3,197,726 7/1965 Hulbert 338-16-8 X 3,201,737 8/1965 Mathison 33-8174 3,233,201 2/1966 Layland 338 3,242,452 3/1966 Grunwald 338-202 X RICHARD M. WOOD, Primary Examiner. J. G. SMITH, Assistant Examiner, 

1. IN A VARIABLE RESISTANCE CONTROL, HAVING A RESISTANCE ELEMENT, AND A CONTACTOR FOR WIPING THE RESISTANCE ELEMENT INTERMEDIATE THE ENDS THEREOF, THE IMPROVEMENT COMPRISING A SPLIT HOUSING COMPRISING A FIRST HOUSING MEANS PROVIDED WITH AN UPSTANDING SIDE WALL OPEN AT ONE END AND CLOSED AT THE OTHER END TO DEFINE A LOWER HOUSING HALF SUPPORTING THE RESISTANCE ELEMENT AND THE CONTACTOR, A RECESS EXTENDING AROUND THE PERIPHERY OF THE UPSTANDING SIDE WALL ADJACENT TO THE ONE END OF THE FIRST HOUSING MEANS AND TERMINATING AT A SHOULDER DISPOSED BETWEEN THE ONE END AND THE OTHER END OF THE FIRST HOUSING MEANS, ONE WALL OF THE RECESS BEING TAPERED TOWARD THE OEN END OF THE FIRST HOUSING MEANS, A SECOND HOUSING MEANS CLOSING THE ONE END OF THE FIRST HOUSING MEANS AND HAVING A DEPENDING SKIRT IN OVERLAPPING RELATIONSHIP WITH A PORTION OF THE UPSTANDING SIDE WALL OF THE FIRST HOUSING MEANS TO DEFINE AN UPPER HOUSING HALF, THE SKIRT OF THE SECOND HOUSING MEANS ABUTTING AGAINST THE SHOULDER OF 